Abstract:

The Bursum Formation of latest Pennsylvanian age was deposited during the final episode of the Ancestral Rocky Mountains deformation in central New Mexico. Over 600 paleocurrent measurements were collected from fluvial strata of the Bursum Formation in the Quebradas region east of Socorro. These measurements, in concert with data from the Bursum Formation for thickness (from outcrops and wells), lithofacies distribution, and maximum clast size provide new constraints on the paleotectonic framework during the Late Pennsylvanian. The long-known Joyita Uplift supplied detritus, mostly recycled from older Pennsylvanian strata, to the northern part of the study area. A major source region exposing dominantly Proterozoic rocks, herein termed the San Antonio Uplift, existed in what is now the southern part of the Socorro Basin of the Rio Grande rift. The San Antonio Uplift contributed arkosic detritus to the central and southern parts of the study area. These two uplifts dominated sediment supply to the western part of a broad region in which the Bursum Formation gradually thickens to the southeast, toward the Pedernal Uplift near Carrizozo. This region formed a weakly subsided saddle-shaped platform between the deep Estancia and Pedernal basins to the north and south. It was not a narrow, symmetrical basin as depicted in previous studies.